Biomass is gaining popularity as a replacement fuel for fossil fuels such as coal, natural gas and petroleum-based products such as fuel oil. The energy stored in a biomass fuel ultimately comes from the same source as fossil fuels, solar energy. The process of photosynthesis captures the solar energy and stores it by creating carbon-carbon bonds. This stored energy can be released by burning or oxidation, breaking the bonds and generating gaseous carbon typically in the form of carbon dioxide. The burning of fossil fuels, therefore, releases carbon into the atmosphere that has otherwise been stored under the earth's surface for millions of years whereas burning of biomass such as wood, corn and other plant material releases gaseous carbon into the atmosphere that was removed only recently through the photosynthetic process.
A number of hurdles exist to utilizing biomass fuels on a widespread basis. For example, storage and conveyance of biomass fuels to the furnace can be a burden that may put off many potential users of biomass fuels. However, a number of biomass fuels, such as most cereal grains, fruit pits, weed seeds, wood pellets, plastic pellets and other pelletized fuels, are easily stored and conveyed.
Dried, shelled corn is often used because of its availability. In addition, dried corn is often much cheaper on a British Thermal Unit (“btu”) basis for generating heat when compared to generating heat using electricity, LP gas, fuel oil and coal. This is especially true where the corn to be burned is not desirable for use in food or feed applications and can be obtained at a discount relative to other higher grade corn. Dried, shelled corn can also be conveyed and transported in a manner that is straightforward and routine due to its use in agricultural settings.
The burning of biomass fuels typically leaves ash and residues in amounts that are greater than fossil fuel burning. Fuels such as corn also leave a slag or clinkers after burning. Mechanisms for removal of these residual materials has been largely operated manually by the user, however newer units are becoming available that make the removal of these residuals more automatic.
Furnaces for burning of biomass and, in particular, corn are known and have been disclosed previously in US20040200394 and US20050208445, the disclosures of which are both incorporated by reference in their entirety. Such corn stoves are available, for example from Nesco, Inc. (Cookeville, Tenn.) under the AMAIZABLAZE trademark. Another such corn stove may be obtained EvenTemp, Inc. (Waco, Nebr.) under the SaintCroix trademark. Yet another such corn stove may be obtained from Bixby Energy Systems (Rogers, Minn.). These corn stoves incorporate features that make corn burning more convenient and reliable, overcoming many of the previously described difficulties associated with burning corn.
Consistent and reliable components for fuel ignition are also important in biomass fuel burning. The fuel must be rapidly and reliably brought to a temperature where the fuel burns, thereby releasing a greater amount of heat energy. One such ignition system that can be employed is an air or gas ignition system in which ambient or pre-warmed air is passed over or brought into contact with a heating element, thereby warming the air to a sufficient temperature to ignite the fuel. The elements are typically disposed within a cover tube. Prior art igniters have used materials that do not provide for optimum durability and conveyance of heat to the fuel. Durability of the tube is especially important where air flow through the tube may be interrupted.
While attempts have been made to overcome the problems described, it would be desirable to have a furnace for burning of biomass materials with an igniter optimized for ignition of such biomass materials.